To clarify the question; as well as getting my match a couple of books from Amazon, I sent one via airmail, for the enjoyment of taking a parcel to the post office (I have my own fun...). Because Amazon fail at 'as few deliveries as possible', both of those are going separately, and only one has been emailed as shipped. So two parcels on their way, and one still sitting in the Amazon warehouse. Do I fill out a new 'confirm shipped' entry for each one, or update the one form, as it's one exchange? Halp.

Your giftee needs to know there's more than 1 package coming, so they know when to expect them, just for convenience sake. On the 'confirm shipped' page you can choose 'add another package' and enter tracking separately whenever it comes available.

I've actually anon-messaged them to make sure they know parcels are coming (and will again, when the last book is shipped). I just don't really know what the 'confirm shipped' form does... if I fill out three, does my match have to confirm all three? That could get tedious, since it's just one exchange.

So it doesn't really matter whether I fill out one 'confirm' form or three, as long as I've confirmed I've shipped something, and they confirm they get something? Got it. I think. I have a daft, today.

As weffey said, it's so redditgifts knows you're being a good santa. Your giftee is encouraged to post about all the packages, but as long as they confirms at least one the system will approve you as a good santa and them as a good giftee.